Inertia locking retractors, of the type disclosed in the U.S. Pat. No. 3,237,729, and applicant's pending application, Ser. No. 303,550 filed Nov. 3, 1972, now abandoned, effect locking of a belt spool upon the occurrence of an inertia force on the vehicle over and above a predetermined minimum. However, such heretofore known and used retractors are unsatisfactory in certain respects, namely, the initial response characteristic of the inertia member is inconsistent, the retractors are relatively noisy due to movement of the inertia response member relative on its conical seat, and the axis of rotation of the belt spool and retractor frame must be orientated in a horizontal plane requiring, in some instances, additional space in a vehicle.